The present invention relates to mixers for mixing dough and other similar viscous materials which are subject to a temperature rise during the mixing process. Preferably bread doughs should be mixed at a temperature of about 78.degree. F. to 80.degree. F. The friction and viscous shear encountered during the mixing process causes a temperature rise, which becomes more severe as the mixing speed increases. Such a temperature rise can cause the dough to become sticky and difficult to process.
A common solution to the above temperature problem is the use of cooled or refrigerated mixing components. Thus, as taught in Kirchoff U.S. Pat. No. 1,778,363, there may be provided a mixing bowl having a chilled breaker tube extending from end-to-end. The dough is directed against the breaker tube by a rotating agitator arrangement and is cooled by water or other cooling fluid directed through the breaker tube. The breaker tube is disclosed as being rotatable, and rotary seal means are provided for circulating the cooling fluid through the breaker tube.
Other means for cooling a dough mixer are disclosed Sticelber U.S. Pat. Nos. 2,415,711 and 2,593,705. Both of these patents disclose a mixing bowl having a curved sheet panel, which is provided with a series of side-by-side channels extending lengthwise along the bowl. The ends of the channels are interconnected to provide a serpentine flow path for a refrigerating liquid pumped from an appropriate source. Sticelber '705 applies the cooling fluid in liquid form to an expansion valve, which is mounted on the mixing bowl.
Another refrigerated dough mixer is disclosed in Smith et al. U.S. Pat. No. 3,155,056 and comprises a pair of rotating paddles mounted within a closed vessel. Means are provided for pumping a cooling fluid through both of the paddles and also through a cooling jacket surrounding the mixing vessel.
Still another prior art dough mixer having temperature regulating means is disclosed in Bandel U.S. Pat. No. 2,931,320. Bandel provides a mixer having a closed vessel having two segregated semi-lunar cooling chambers extending lengthwise along the length of the mixer. Bandel also provides cooled end walls. Another prior art mixer having temperature controlled means is disclosed in Jensen U.S. Pat. No. 1,213,879. Jensen deals with treatment of liquid materials, which are quite different in nature from dough. The disclosed apparatus is said to be suitable for fermenting or ripening milk. The arrangement includes a rotating agitator comprising a pair of independent spiral ducts. Temperature control fluids are independently pumped through such ducts via rotary seals at the ends of the agitator.